Production of glycerine



Oct. 22, 1957 K. B. coFl-:R

PRODUCTION oF GLYcI-:RINE

Filed April 19, 1954 mQUoLmmD Ew Een@ om Unified rates Patent PRODUCTION F GLYCEREE Kenneth B. Cofer, Pasadena, Tex., assignor to Shell De velopment Company, New York, N. Y., a corporation of Delaware Application April A19, 1954, Serial No. 424,16)

6 Claims. (Cl. 260-635) This invention relates `to the conversion of glycerine epihalohydrins, that is, the 1halo2,3epoxypropanes, to glycerine. It deals with an improved process for carrying out this hydrolysis whereby the formation of undesirable by-products is suppressed and high yields of glycerine are obtained in an economical and eflicient manner.

A number of diiferent methods have been proposed for synthesizing glycerine. The more successful of these methods depend upon the hydrolysis of mono and dichlorohydrins. Aqueous metal hydroxide solutions, preferably buiered with a salt of a strong base and a Weak acid such as sodium carbonate, are used as the hydrolyzing agent. All of the prior methods have disadvantages of one kind or another in commercial scale operation. By-product formation, especially the formation of higher molecular products such as polyglycerols, is a serious disadvantage. Not only is the yield of glycerine reduced thereby, but also recovery of the glycerine in a pure form may be rendered more difficult as a result. Excessive consumption of reagents and relatively slow reaction making necessary the use of large and expensive reactors are other drawbacks which frequently accompany the methods previously suggested. A further disadvantage of such methods is the need for operating with aqueous solutions of low concentration which makes it necessary to evaporate large amounts of water in order to recover the glycerine in usable form, thus increasing its cost.

It is an object of the present invention to avoid the foregoing disadvantages of prior methods of producing glycerine. Another object is the provision of an etlicient method for producing glycerine from 1-halo-2,3epoxy propanes. Still another object is the hydrolysis of 1- chloro-2,3epoxypropane under conditions at which glycerine is produced in high yields and in relatively high concentrations which simplify its recovery. Further objects and advantages of the process of the invention will be apparent from the following description of some of the methods which are suitable for carrying it out.

In accordance with the invention, the foregoing and other objects are achieved by carrying out the hydrolysis of 1-halo-2,3-epoxypropanes by short contact at high temperature and pressure with aqueous inorganic carbonate salt solution. The reaction is carried out at a temperature of 130 C. to 200 C. and under pressure of carbon dioxide in the range of 100 to 500 p. s. i. g. for a time of about 5 to 20 minutes. Optimum temperature and residence time vary somewhat with the glycerine concentration of the nal, completely hydrolyzed product, as can be seen from the following gures:

Temperatures and residence times above these optimum ranges promote excessive polymer formation. Those below the optimum ranges lead to incomplete hydrolysis. Temperature and residence time are dependent variables. 'lhe optimum ranges given define the limits within which an adjustment of one variable with respect to the other will give the best yield. Usually residence time is controlled by the volume of the reactor and the product throughput required. Optimum yield is then obtained by adjustment of the reaction temperature.

By this method of operation virtually complete conversion of the 1halo2,3epoxypropane can be achieved with very little by-product formation. The reaction can be carried out advantageously with haloepoxy-propane solutions of relatively high concentration. Advantageously, aqueous solutions containing about 15% to 30% by weight of 1chloro2,3epoxypropane are used. In contrast with prior methods of operation, formation of high boiling materials at these high concentrations is very small in the new method. At these concentrations correspondingly concentrated solutions of glycerine are obtained, thus materially reducing the amount of water which must be evaporated in recovering the product.

In addition to improved glycerine yields, an important advantage of the new method over prior practice is the material improvement in alkali economy which it gives. Preferably the process is carried out with an amount of inorganic carbonate such that 2% to about 20%, most preferably about 15% to about 20%, in excess of the stoichiometric requirements remains after completion of the reaction. Smaller amounts of carbonate can be used but less complete hydrolysis usually results, especially when less than 10% excess is employed. Larger amounts of inorganic carbonate do not improve the yield of glyc- 'erine and increase the load on the salt removal facilities.

The efficiency of inorganic carbonate utilization is further increased by operating with higher concentrations of l-halo-2,3epoxypropane. Thus, it has been found that, while maintaining the optimum 15% to 20% excess of sodium carbonate in the product, the consumption of 'sodium carbonate fell from 79 pounds to 71 pounds per hundred pounds of glycerine produced when the glycerine concentration was increased from 15% to 25% by weight in the eiuent, other conditions being the same and within the previously indicated ranges. This unexpected improvement is believed to be possibly .attributable to reduced solubility of non-glycerine precursors in the reaction media at higher concentrations with resulting reduced reactivity of these impurities with carbonate.

Carbonates such as sodium carbonate have been suggested as the equivalents of other basic agents such as sodium hydroxide, etc. in the hydrolysis of hydroxy halides. They are not equivalents of such other bases in the hydrolysis of 1-halo-2,3epoxypropanes, however, and such other bases cannot be substituted for the carbonates used in the present process without sacrifice of important advantages of the invention. To achieve the desired results, inorganic carbonate or bicarbonate salts or mixtures thereof, all of which are included in the term inorganic carbonate as used herein generically, must be employed as the essential hydrolyzing agent. The carbonate ion is an important factor responsible for reduced by-product formation as Well as for the rapid catalysis of the hydrolysis and hydration reactions. The carbon dioxide from the reaction may also act as a catalyst as well as a bufIer to prevent high pH, which promotes excessive polymer formation. This does not, of course, preclude the use of such minor amounts of other basic agents as Y Vpolymer formation.

geously produced by absorbing carbon dioxide liberated in do not essentially alter the reaction or change it substamf tially from that produced when inorganic carbonates are used as the sole hydrolyzing agent. Thus, for example, more than about %-15% by weight of sodium hydroxide in the total alkali fed leads to undesirably increased The carbonate may be advantathe reaction `in caustic soda solution, for which purpose a small excess of sodium hydroxide is desirable.

The preferred inorganic carbonate 'salts' for use in the process of the invention are'- the'v alkali metal carbonates and bicarbonates. Sodium. carbonate and bi-Y carbonate are Yespeciallykuseful bec'a'usej of their low cost and good solubility in the reaction irrediurn.V A1- kaline earth metal carbonates can b'e' used but vare less desirable because of their 'low'rsolubility t The process has been found to'be especially useful in the hydrolysis of lchloro-2,3'epoxypropane tor-glycerine. It has been .used eectivel'y, however, lfor the hydrolysis of' l-bromo-2,3epoxyprop'ane and otherV l/-halo-Z- epoxypropanes Lcan be similarly used. The vstarting 'i1- range of 130 C. to 200 C. as previously'V indicated.

Thev thus preheated mixture, under a pressure of 100 to 500 Y'quired reactor volume.

halo-2,3-epoxypr'opane fcan'be formed in the 'reaction mixture from 'the 'corresponding'dihalo yhydroxypropanes. It' is 'only necessary in such cases to increase the'amount of .'sodiu'm carbonate Vused by one-half mole for each additional equivalent' `of halogen present. Mixtures of t dichloro'hydrins and epichlorohydrin, for instance, those described in Tymstra'patent-U.V $2,605,293, are Suitable feed sto'cks for the new. process. Y

Various'proce'dures ca'n be used in carrying out the process. It can' b'e' conducted batchwise, intermittently, 'or continuously.' For the preferred continuous method of operation one can' use a reactor which may, if desired, be filled with Raschig rings or other suitable inert packing or may be an unpacked Vessel. The reactor can be ar horizontal vessel or of the vertical type,- in which case the haloepoxypropane or its precursors and theaqueous sodium carbonate solution to. be reacted therewith ycan be fed through the reactor in either upow or downiiow. An unpacked reactor constructed of passes or coils ofrpiping loffers advantages, particularly in pro- Yyiding' good'temperatur'econtrol in the reaction. In such a tubular reactor a gradual temperature rise as thereaction progresses can be advantageously maintained. More effective utilization of the inorganic carbonate is obtained with' such reactors, apparently due to minimized backmixing and resulting suppression of side reactions between the sodium carbonate` and impurities in the feed. Formation of undesirable high boiling luy-products is also inhibited in'tubular type reactors through Yminimized backmixin'g ofA glycerine with incompletely hydrolyzed reaction mixture.' One can alsouse 'a combination of a tubular' reactor with a'tank 'reactor in which the initial stages Yof the4 reaction, corresponding to that taking place in, say, about the first one-fifth to about onethird'of the total reactor volume in which a major portion bonate solution introduced by line `3, to pump 44 from Il:

which passed to preheater V5. In this preheater, as shown, the feed mixture `is heated by indirect heat trans-v ferY from' steam introduced by line 6, the, condensate from which is withdrawn by lin'e'7. Other heating media can, of course, be employed. The th'us heated reaction mixture withdrawn by line 8 can be further heated'by direct injection of high pressure steam introduced by line Heating by direct injection' of steam canbe used alone to bring the reaction mixture :to the desired temperature Within the p. s. i. g. suiicient to maintain a liquid phase system, is fed to reactor 10 containing a suicient number of passes of pipe 11 to provide about one-fourth of the total re- Eluent from reactor 10, still at reaction temperature and pressure, Vpasses Vby line 12 to tank-type reactor 13 in which the hydrolysis is com'r pleted. A total residence time of about 5 to 15 minutes in reactors 19 and 13, which are advantageously insulated to conserve heat and can be provided with additional Y heating Vmeans if desired, is suitable. Thel reacted mixture is taken off by line 14,lcontaining pressure reducing Valve 15,10 ashdrum 16 in which carbon dioxide is separated and removed by line 17 from aqueous glycerine solution taken off by line 18. Vrlhe excess sodium carbonate in the glycerine solution is neutralized with acid introduced by line 19 in neutralizer 20 from which the solution is taken oi by line 21 and fed to evaporation and distillation units 22 and 23. The salt produced is removed conventionally and talrren off by line 24, while the water and low boiling impurities are taken off by line 25 and the high boiling impurities by line 26. The product glycerine is recovered by line 27.

The carbon dioxide taken off by lineV 17 fromthe ash drum 16, together Ywith carbon dioxide removed by line' 28 from neutr'alizer.' 20, Yis' fed to absorber 29. In the absorber the gaseous carbon dioxide isV passed counter-V current to sodium hydroxide solution introduced byline 30. They resulting sodium carbonate solution is withdrawn by li'ne 31 l and Yreturned to the reaction by line 3 together withl make-up sodium Vcarbonate solution supplied by line 32 in' an amount sufficient to provide one equivalent of base .per equivalent` of reactive halogen in the feed stream" from tank"1and preferablyv about 5%' to 20% in-excess of such stoichiometric requirement.

By this method of operation, the amount of base re quired,'i. e. sodium hydroxideV supplied by line 30 and sodium Vcarbonate fed by lineV 32, is 20% to 35% less Vthan when the hydrolysis kis carried out'with buffered reduced formation of undesirable high boiling products Y which are only M0 to 1A; of the amount previously produced.

The following examples illustrate these and other advantages of the new process as applied to the hydrolysis of 1'chloro2,3epoxypropane. y

Y EXAMPLE 1 y l-chloro-2`,3epoxypropane (produced by steam strip'- ping an allyl chloride chlorohydrination Vproduct; in the presence of a base), analyzing'about 75% by Weight lchloro-2,3epoxypropane, was used as feed to a pipe reactor constructed of-l00 feet of 6-inch steel pipe arranged'in a vertical stackzof four horizontal passes-in series. The l-chlor'o-2,3epoxypropane and aqueous sodium carbonate feed streams were mixed'in a manifold on the suction side of a reactor feed pump and charged to the reactor at p. s. i. g. Heat for the reaction was supplied by direct injection of 175 p. s. i. g. steam ata point about four feetvdownstream from the feed inlet. Product from the reactor was reduced to atmospheric pressure andthe aqueous glycerine separated from the'carbon dioxide. The carbon dioxide was absorbed in sodium hydroxide solution to produce sodium carbonate for further hydrolysis, and the aqueous glycerine solution was neutralized, evaporated and distilled to obtain pure, refined glycerine. The following are typical results obtained in runs at different concentrations of 1-V ch1oro-2,3epoxypropane expressed as concentration of equivalent glycerine vin the reacted mixture, using the reaction conditions in the ranges Lfou'nd to be 'optimum Vfor these concentrations:

Equivalent Glycerine Concentrations Temperature, C 154-166 157-180 163-180 Residence Time, minutes V 8-15 7-9 8-10 Excess NazCOg in Product, percent w- -20 15-20 15-20 Glycerine Conc. in Product, percent w- 13-18 20-25 .Alkali Consumption, lbs. N agCOa Fed/ 100 lbs. Glycerine Produced 81-84 76'79 (i442 NaCl/Glycerine Ratio in Product 1.10 O. 71 0.67 H2O] Glycerine Ratio in Product 18. 0 5. 0 2. 5 YiFeltcl1 (Percent Glycerine Precursors Glycerine 98. 5 98. 5 -97. 1 Polymer 1. 3 1. 0 2. 6 Unhydrolyz 0. 2 0.5 0.3

The temperatures Vreferred to herein and in the appended claims are the maximum temperatures attained 'during the reaction. Some reaction takes place at the lower temperatures at which the reactants are mixed and pumped to the reactor before the nal heating to the specied're- 5 sodium carbonate .in a manifold in the suction side of a single stage, kdouble suction centrifugal pump capable of developing 1465-4175 pounds pressure. The pump served to mix and disperse the reactants as Well asV to pressure'. the unit. The pump discharged into th'e'bott'oin of the l0 reactor which operated near `l50 p. s. i. g. Heat Ato the reactor was supplied by injection of '717'5-p'oun'd jsteam into the bottom of the unit and by heat of reaction. Product Withdrawn'from the top of the reactor Was'r'outed through back-pressure controller into Ya phase separator 15 where the 'aqueous glycerine product was separated frorm the carbon dioxide. The product layer was removed for analysis and recovery of the glycerine, and 'the carbon dioxide was absorbed in sodium hydroxide Yto produce sodium Acarbonate solution for further hydrolysis.

Vertical zta'nk Vreactor Excess sodium carbonate." .16%-20% lby weight.

action temperature is carried out. Yi 1d L ss l G1 Germ The residence timesreported in the foregqing table oiyc'erme 'Pfecursor redyer-e are calculated by dividing the reactor volume in gallons Maxlm'lm Temperature CJ Ctlpncgtra- 'centw by the feed rate in gallons per minute. The actual liquid .twf residence time in the reactor is somewhat lower due to 171111135350- P] ,er the reactor volume occupied by the carbon Adioxide liber- Mterial ym ated during the reaction.

5.6 3.a 1.7 EXAMPLE II 5.0 1.3 1.9 Tests of batch hydrolysis were made in a high pressure, j g1g 'stainless steel reactor provided with a high speed mixer and an internal heating coil. The reactor was charged with 1Giyceriiie yieid=ioo-(unhydroiyzeu mater1a1+ polymer). aqueous sodium carbonate solution which was heated, Pipe reactor then the l-chloroZ-epoxypropane (7S-9% potenqal Reaction ma 6.9-9.3 minutes, glycerine) was added and the reactor closed. The nux- Excesssodium garbormte .16% 23% .byweight ture at 80 C.90 C. was then heated 'to the reaction Y v temperature. v When the evolved carbon dioxide has raised 40 Yield Lossilyrme the pressure in the reactor to the desired level, the pres- Maximum Tem Emme (OVC) "Y Precurgtiersure was maintained constant for the remainder of the p' Y tion (per. v' reaction period by releasing gas through a bleed-ofi valve Cent WJ Unhydro- .to a scrubber in which the carbon dioxide wasabsorbed me@ polymer in 20% sodium hydroxide solution. The glycerin'e yield 45 Mammal was determined from analyses of the -feed stream, reactor product, reactor wash Water, and the vent scrubber solu- 12-.8 0-5 0 9 13.2 0.5 i 5 tion, after which hydrolyzer product Was Worked up in 15,7 0 3 1 6 the usual Way for recovery of pure glycerine. 186 ,35 @-2 2 8 2.4 0.3 3 9 The following are the results of typical runs under dif- .50 n ferent TeaCIOD CondltlonslGcerlyine y'ield='100(unhydrolyzed material polymer).

Feed Composition (Per- Unhydrocent W.) Stoichio- Maxi- Maxilyzed 'High Glyc. metric mum mum Reaction Glyc. Pre Boiling Yield Excess of Reaction Reaction Time'1 cursors Product (Percent 1-Chloro- Sodium NagCOi, Temp. Pressure (min.) V(Percent '(-Percent Vw.) 2,3epoxy- Carbon Water Percent C.) (p. s. i. g.) w.) w.)

propane ate 10.1 6. 4 s3. 7 5 162 47o 15 1. 8 1:3 97. s 15. o s. 6 76. 0 2 16o 450 15 3. 6 0.4 97. 2 20. o ii. 5 6s. 5 None 165 400 15 0. 4 2.8 97.54 2o. i 11. 7 6s. 2 2 165 42o i5 -Noiie 2.2 97. 3 25.0 i4. 3 60.7 None 15s 36o 15 1.7 0. 5 9s. o 24. 7 14. 9 6o. 4 163 45o 15 None 6:3 9s. 6 24.6 15. 4 60.0 1o 161 445 15 1. o 1.1 Y96. 6 24. 5 14.9 6o. 6 5 153 20o 15 None 99. o 24. 6 15. 5 59. 9 10 152 41o 16 None 99. 2

1 Reaction time is the total residence time in the reactor including the heat-up time.

EXAMPLE III The effect of variations in the maximum operating temperature upon the results of hydrolysis of mixtures of 1chloro-2,3epoxypropane (75 %-80%) with about 20%- 25% of glycerine dchlorohydrins was determined in two series of tests under different conditions. One series of tests was made in the tubular reactor used in Example I EXAMPLE IV and the other tests were carried out in a tubular reactor tank reactor used in Example III.

. w YieldLoss,Glyc i Glycerine Excess crine Precursors Residence.'1`ime in Re- Concentra- Sodium Fed (Percentw.) actor (mins.) tionin Carbonate r Product Used (Per- 1.. (Percent cent w.) Unhydroi Y w.) lyzed Polymer Material Pipe reactor: 6.7 l 5.2 9.7 2.9 0. Tankreactor' t e f EXAMPLE v The .electY of theamount Vof excess sodium carbonate used in carrying out the hydrolysis of the impure lchloro 23-epoxypropane employed in Example III is shown by the following results obtained in the reactors described in Examples I and 111.

`Vertical ttmk reactor Maximumftemperature 157 166 C. Glycerine concentration in eluent 4%-6%. Residence time 10-16 min.

l VYield Loss, Glycerine Precursors Fed (Percent w.) Excess Sodium Carbonate (Percent w.)

Unhydrolyzed Polymer Material Pipe reactor VMaximumY temperature 162182 C. Glycerine concentration in eluent 20%-27%. Residence time 7-11.5 min.

Yield Loss, Glycerine Y Precursors Fed (Percent w.) Excess Sodium Carbonate (Percent w.)

aber@ P 1 yze o ymer Material perature of 130 C: to 200 C. in the'presence of carbonv dioxide under 'a pressure in the range of 100101500 p, s. Lrg. suicent to maintain the reactants'in the liquid phase for about 5 to 20 minutes, and recovering glycerine from the resulting reaction mixture.

2. A process in accordance with claim l wherein alkali y metal carbonate hydrolyzing agent is used in an amount of about 2% to 20% in excess of the stoichiometric requirement for the hydrolysis. f Y j A 3. A process inl accordancewitheclaiml wherein the reaction is carried out with an aqueous solution containing about 15% to 30% by Weight of 1chloro-2,3epoxyl propane.

4. A process'for producing glycerine which comprises hydrolyzing l-chloro2,3-epoxypropane by contactwith an aqueous solution Ycontaining at least a Stoichiornetric amount of4 sodium carbonate as the essential hydrolyzing agent atf a temperature of. 150 C. to 180 C. in the presence of carbon dioxide under a pressure in the range of 100 to 500 p. s. i. g. suiiicientto maintain the reactants in the liquid phase forabout 5 to l5 minutes. A 5.A pr,ocess in aocordance'with Vclaim 4 wherein the reaction is carried out with about 10% to 20% excess of sodium carbonate above the stoichiometric requirement for hydrolysis of the starting material.

6. A process in` accordance with claim 4 wherein the reactionis carried out with an aqueous solution containing propane.Y T I References Cited in the Ytile of thisl patent i Y UNITED STATES PATENTS 

1. A PROCESS FOR HYDROLYZING A 1-HALO-2,3-EPOXYPROPANE WHICH COMPRISES CONTACTING THE 1-HALO-2,3-EPOXYPROPANE WITH AN AQUEOUS SOLUTION CONTAINING AT LEAST A STOICHIOMETRIC AMOUNT OF AN INORGANIC CARBONATE OF THE GROUP CONSISTING OF THE ALKALI METAL AND ALKALINE EARTH METAL CARBONATES AS THE ESSENTIAL HYDROLYZING AGENT AT A TEMPERATURE OF 130*C. TO 200*C. IN THE PRESENCE OF CARBON DIOXIDE UNDER A PRESSURE IN THE RANGE OF 100 TO 500 P.S.I.G. SUFFICIENT TO MAINTAIN THE REACTANTA IN THE LIQUID PHASE FOR ABOUT 5 TO 20 MINUTES, AND RECOVERING GLYCERINE FROM THE RESULTING REACTION MIXTURE. 